1. Field of Invention
Embodiments of this invention relate to the field of Internet Protocol (IP) networks, Transmission Control Protocol (TCP) and out-of-band signaling and peer-to-peer networking.
2. Discussion of Related Art
Transmission Control Protocol (TCP) is one of the main protocols in the Internet and TCP/IP networks. TCP is a connection-oriented protocol where the devices at the end points (i.e., peers) use a preliminary protocol to establish an end-to-end connection before any data is sent. Connection-oriented protocol service is sometimes called a “reliable” network service, because it guarantees that data will arrive in the proper sequence. The alternative to connection-oriented transmission is the connectionless approach, in which data is sent from one end point to another without prior arrangement, for example, user datagram protocol (UDP). A TCP connection contains three phases: connection establishment, data transfer and connection termination.
In the connection establishment (or call setup) phase of any connection-oriented protocol, control data is passed between the two endpoints to establish a connection or circuit.
This control traffic (or signaling) may occur on the same channel used for data exchanged (in-band signaling) or done on a separate channel that is dedicated for the purpose (out-of-band signaling). The TCP protocol uses a Three Way Handshake protocol to synchronize and establish a connection between two TCP peers. In the connection establishment phase, the exchange of signaling (Three-way-handshaking) traffic is sent on same TCP connection (or channel) that is used for data transfer. While TCP uses in-band-signaling, most circuit switched communication use out-of-band signaling as specified in the Signaling System 7 (SS7) standards.
The TCP Three Way Handshake protocol between a client and server is shown in FIG. 1. A TCP connection is identified by the IP addresses and virtual port numbers used by both ends. During communication, additional numbers are used to keep track of the order or sequence number which indicates what order the segments of data should be reassembled. Finally, a maximum transmission size is constantly being negotiated via a fallback mechanism called windowing. The combination of port numbers, sequence numbers and window sizes constitutes a TCP connection and once these parameters have been negotiated between the TCP endpoints a TCP connection is established.
In the TCP/IP protocol suite, TCP 205 is the intermediate layer above IP 206 and below the application 204 as in FIG. 2. Applications send streams of 8-bit bytes to TCP for delivery through the network, and TCP divides the byte stream into appropriately sized segments. TCP then passes the resulting packets to IP for delivery through an Internet 202 to the TCP module 208 of the other endpoint 203. The TCP module 208 at the far end sends back an acknowledgement for bytes which have been successfully received; a timer at the sending TCP will cause a timeout if an acknowledgement is not received within a reasonable round trip time, and the (presumably lost) data will then be re-transmitted. The TCP checks that no bytes are damaged by using a checksum; one is computed at the sender for each block of data before it is sent, and checked at the receiver. Since each module has no knowledge of the function of the layer below or the layer above and since IP is a datagram network, IP packet that form the TCP connection may be received from different network interfaces.
In certain environments all or part of the TCP signaling traffic may be lost before reaching one or both TCP endpoints, leading to no connection establishment or slow page download times. Loss if signaling traffic may occur (but not limited to) when there is one or more firewalls present in the communication path between the TCP endpoints or when the TCP signaling traffic is traveling over unreliable wireless link. In the case of having firewalls present in the communication path, no connection is establishment since the firewalls typically bock all incoming TCP signaling traffic. In the case of having an unreliable link, the page download time can be hampered since a page download use parallel TCP connections to download the set of objects that comprise a page. The loss of TCP signaling traffic adversely impacts the total page download more than the loss of data packets since the delay to re-open a TCP connection is much greater than the retransmission delay for a data packet. This invention of out-of-band signaling for TCP connection setup can be used to improve performance over unreliable links and be used to set up and establish TCP connections when otherwise not possible.
Embodiments of this invention include the use of out-of-band signaling for synchronizing and establishing a connection between two TCP endpoints. Embodiments of this invention provide a system to enable out-of-band signaling for TCP synchronization and connection establishment between two TCP endpoints. In embodiments of this invention, the control channel used for the out-of-band signaling traffic between the TCP endpoints (or peers) is achieved using a system that consists of a signaling broker, an agent application, and a virtual network interface and capture module that together create control channel for the TCP signaling traffic.